Observations of sintering of fine particles of diamond, SiO2and Al2O3and possibly Al in a neutron radiation field are reported. Possible mechanisms are discussed and it is concluded that the transport of interstitials to the surface is most probably the responsible mechanism. This may occur by diffusion, channeling or focusing, and it is suggested that measurement of radiation sintering at two temperatures will show if the effect is thermally activated diffusion and that examination of changes in stoichiometry of the sintered interface will show if focusing or channeling dominates as a transport mechanism. Computations are also presented which show that the solar wind on the lunar surface could sinter dust into the observed clumps in a reasonable length of time.